Utility of light-emitting diode microscopy for the diagnosis of pulmonary tuberculosis in HIV infected patients

ObjectiveTo determine the utility of light-emitting diode fluorescent microscopy (LED-FM) for the diagnosis of pulmonary tuberculosis (PTB) in HIV-infected patients.Material and methodsA cross-sectional study was performed on 400 HIV-infected, clinically or radiologically suspected PTB patients. Two sputum specimens were collected from each patient. Two direct smears were prepared from each sputum specimen. One was stained by ZN method and another by auramine-O method and reported as per the Revised National Tuberculosis Control Programme (RNTCP) guidelines. LED-FM stained smears were reported by two readers. All specimens were cultured on LJ medium after digestion and decontamination. Address and contact details of all the patients were recorded in case record form. They were contacted for follow-up if required.ResultsOf the 800 sputum specimens processed, 130 were positive by LED-FM method and 33 were positive by ZN method; 77 specimens showed growth of MTB on LJ medium. When compared with solid culture as a reference standard, LED-FM has a sensitivity of 67.53%, specificity of 88.71%, PPV of 40% and NPV of 96.08%. Seventy-eight LED-FM positive and culture negative specimens had scanty grading. Of these, 15 were confirmed as having PTB as they responded to anti-TB treatment. The concordance between two readers was 98.75%.ConclusionLED-FM can be a good screening test for the diagnosis of PTB in HIV-infected patients. However, all scanty grade positive smears need to be confirmed by WHO approved gold standard.